V-Band Sub-Harmonic Gate-Pumped Resistive Mixer with a 180° Hybrid Using an In-Phase Power Divider Merging with an Out-of-Phase Marchand Balun
A high isolation gate-pumped resistive sub-harmonic mixer with a miniature 180° hybrid is demonstrated using 90 nm CMOS process. An in-phase power divider and an out-of-phase Marchand balun form a reduced-size 180° hybrid with shared coupled lines. For a sub-harmonic mixer, the input matches at LO/RF ports of the 180° hybrid are achieved using high/low coupling coefficients of the shared equal-length coupled lines. Moreover, isolations between RF and LO ports are achieved at all frequencies because a Marchand balun maintains balanced signals and a power divider provides in-phase equal magnitude signals at all frequencies. The sub-harmonic mixer achieves a conversion gain around 0–3 dB from 58–67 GHz with 0 dBm LO pumping power. The LO-to-RF isolation is better than 36 dB within the operating bandwidth.